A low elastic modulus Ti-Nb-Hf alloy bioactivated with an elastin-like protein-based polymer enhances osteoblast cell adhesion and spreading.

ABSTRACT

ß-type titanium alloys with low Young's modulus are desirable to reduce stress shielding effect and enhance bone remodeling for implants used to substitute failed hard tissue. For biomaterials application, the surface bioactivity is necessary to achieve optimal osseointegration. In the previous work, the low elastic modulus (43 GPa) Ti-25Nb-16Hf (wt %) alloy was mechanically and microstructurally characterized. In the present work, the biological behavior of Ti-25Nb-16Hf was studied. The biological response was improved by surface modification. The metal surface was modified by oxygen plasma and subsequently silanized with 3-chloropropyl(triethoxy)silane for covalent immobilization of the elastin-like polymer. The elastin-like polymer employed exhibits RGD bioactive motives inspired to the extracellular matrix in order to improve cell adhesion and spreading. Upon modification, the achieved surface presented different physical and chemical properties, such as surface energy and chemical composition. Subsequently, osteoblast adhesion, cell numbers, and differentiation studies were performed to correlate surface properties and cell response. The general tendency was that the higher surface energy the higher cell adhesion. Furthermore, cell culture and immunofluorescence microscopy images demonstrated that RGD-modified surfaces improved adhesion and spreading of the osteoblast cell type.